The present touch technologies basically are categorized to several types: impedance, capacitance, light sensing, electromagnetic, supersonic and liquid crystal display (LCD) in-cell; wherein the LCD in-cell can be further categorized to: impedance, capacitance and light sensing. In a display adopting a light sensing in-cell touch panel, the determination of a light sensing apparatus whether or not is being switched-on, so as to further determine whether or not the LCD in-cell is being touched, is based on the leakage current variation caused by different light intensities emitted thereon.
For example, a light sensing apparatus primarily is implemented with thin-film transistors, and the thin-film transistors each may have various leakage currents in response to various light intensities emitted thereon. For example, the leakage current may have a first current value, a second current value and a third current value when the light sensing unit is being touched by an object (for example, a finger), emitted by an environmental light and emitted by a light from a light pen, respectively. Because the leakage current is proportional to the light intensity, accordingly the first current value is smaller than the second current value and the second current value is smaller than the third current value. In addition, a light sensing apparatus further includes an integrator, which is configured to convert the charges derived from the leakage current into an output voltage. Thus, the light sensing in-cell touch panel can determine that whether or not the associated thin-film transistor is being touched according to the output voltage. However, once the light sensing apparatus has been used for a relatively long time, the voltage difference between a gate and source terminals of the light sensing apparatus may have an offset and thereby changing the light sensing apparatus's light sensing characteristics; and thus, consequently a sensing result error is resulted in.